DEA/NO-stimulated adenosine accumulation is resistant to the 5′-nucleotidase inhibitor guanosine monophosphate. Cultures were exposed to DEA/NO (D/NO; 100 μm) with or without 500 μm GMP for 30 min. The presence of GMP had no significant effect on the accumulation of adenosine or on the basal level of adenosine. The experiment shown is a representative experiment of four that were performed.